PM / Hibernate: Add sysfs knob to control size of memory for drivers

Martin reports that on his system hibernation occasionally fails due
to the lack of memory, because the radeon driver apparently allocates
too much of it during the device freeze stage.  It turns out that the
amount of memory allocated by radeon during hibernation (and
presumably during system suspend too) depends on the utilization of
the GPU (e.g. hibernating while there are two KDE 4 sessions with
compositing enabled causes radeon to allocate more memory than for
one KDE 4 session).

In principle it should be possible to use image_size to make the
memory preallocation mechanism free enough memory for the radeon
driver, but in practice it is not easy to guess the right value
because of the way the preallocation code uses image_size.  For this
reason, it seems reasonable to allow users to control the amount of
memory reserved for driver allocations made after the hibernate
preallocation, which currently is constant and amounts to 1 MB.

Introduce a new sysfs file, /sys/power/reserved_size, whose value
will be used as the amount of memory to reserve for the
post-preallocation reservations made by device drivers, in bytes.
For backwards compatibility, set its default (and initial) value to
the currently used number (1 MB).

References: https://bugzilla.kernel.org/show_bug.cgi?id=34102
Reported-and-tested-by: Martin Steigerwald <Martin@Lichtvoll.de>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

1 files changed, 4 insertions, 0 deletions

diff --git a/kernel/power/power.h b/kernel/power/power.h
index 03634be55f62..9a00a0a26280 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -15,6 +15,7 @@ struct swsusp_info {
 
 #ifdef CONFIG_HIBERNATION
 /* kernel/power/snapshot.c */
+extern void __init hibernate_reserved_size_init(void);
 extern void __init hibernate_image_size_init(void);
 
 #ifdef CONFIG_ARCH_HIBERNATION_HEADER
@@ -55,6 +56,7 @@ extern int hibernation_platform_enter(void);
 
 #else /* !CONFIG_HIBERNATION */
 
+static inline void hibernate_reserved_size_init(void) {}
 static inline void hibernate_image_size_init(void) {}
 #endif /* !CONFIG_HIBERNATION */
 
@@ -72,6 +74,8 @@ static struct kobj_attribute _name##_attr = {	\
 
 /* Preferred image size in bytes (default 500 MB) */
 extern unsigned long image_size;
+/* Size of memory reserved for drivers (default SPARE_PAGES x PAGE_SIZE) */
+extern unsigned long reserved_size;
 extern int in_suspend;
 extern dev_t swsusp_resume_device;
 extern sector_t swsusp_resume_block;